Phase transition kinetics in austempered ductile iron (ADI) with regard to MO content

Martin Landesberger, Robert Koos, Michael Hofmann, Xiaohu Li, Torben Boll, Winfried Petry, Wolfram Volk

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The phase transformation to ausferrite during austempered ductile iron (ADI) heat treatment can be significantly influenced by the alloying element Mo. Utilizing neutron diffraction, the phase transformation from austenite to ausferrite was monitored in-situ during the heat treatment. In addition to the phase volume fractions, the carbon enrichment of retained austenite was investigated. The results from neutron diffraction were compared to the macroscopic length change from dilatometer measurements. They show that the dilatometer data are only of limited use for the investigation of ausferrite formation. However, they allow deriving the time of maximum carbon accumulation in the retained austenite. In addition, the transformation of austenite during ausferritization was investigated using metallographic methods. Finally, the distribution of the alloying elements in the vicinity of the austenite/ferrite interface zone was shown by atom probe tomography (APT) measurements. C and Mn were enriched within the interface, while Si concentration was reduced. The Mo concentration in ferrite, interface and austentite stayed at the same level. The delay of austenite decay during Stage II reaction caused by Mo was studied in detail at 400C for the initial material as well as for 0.25 mass % and 0.50 mass % Mo additions.

Original languageEnglish
Article number5266
Pages (from-to)1-23
Number of pages23
Issue number22
StatePublished - 2 Nov 2020


  • ADI
  • Atom probe tomography
  • Dilatometry
  • Molybdenum
  • Neutron diffraction
  • Phase transition kinetics
  • Retained austenite


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